HP 8642A Operating Manual page 284

Performance Tests
Model 8642A/B
PERFORMANCE TESTS
NOTE
Be sure the HP 8642 has had 10 days to warm up
before beginning the test. If the HP 8642 was
disconnected from the power line for less than 24
hours, only a 24 hour warm-up is needed.
PROCEDURE: 1. Set the rear panel REFERENCE switch to INT.
2. Connect the instruments shown in Figure 4 - 1 8 .
3. Adjust the oscilloscope's controls for a stable display of the 10 MHz
output.
4. Measure the time required for a phase change of 360 degrees. Record
the time (Tl) in seconds.
T l = s
5. Wait for a period of time (from 3 to 24 hours) and re-measure the
phase change time (T2). Record the period of time betwen
measurements (T3) in hours.
T2 = g
T3 = h
6. Calculate the aging rate from the following equation:
Agi
„
g
^ . {+**.) (_L. _ JL_) ( JL_)
where: 1 cycle = the phase change reference for the time
measurement (in this case 360 degrees)
f = 8642's reference output frequency (10 MHz)
T = specified time for aging rate (24h)
T l = initial time measurement(s) for a 360 degree (1 cycle) change
T2 = final time measurement(s) for a 360 degree (1 cycle) change
T3 = time between measurement (h)
4 - 5 2